|The elevation of Long Pine Key is only about three feet above sea level, but in the Everglades that is high ground. The term "key" in this case refers to the island-like outcropping of limestone rock that surfaces above the surrounding wetlands. Your class will visit two habitats in the Long Pine Key area after lunch.|
Unlike slough and sawgrass marsh, the pinelands and hammock habitats are typically dry underfoot. (Standing water can usually be found only in solution holes, depressions scattered in the limestone rock.) The uneven rock layer you're walking over here is a continuation of the Atlantic Coastal Ridge, a relatively high geologic feature that follows the Atlantic shoreline in Broward and Dade Counties before ending southwest of Long Pine Key near Mahogany Hammock. Early Miami, and the first roads and railroads in South Florida, were all built on the Atlantic Coastal Ridge.
The Long Pine Key picnic area is set in a stand of Dade County slash pine. Slash pines grow throughout Florida, but the Dade County subspecies has especially dense, sturdy wood. What do you think happened to this habitat as Miami grew? Slash pines were used for lumber, and the high ground pineland habitat now is mostly covered by homes and parking lots. Even the Long Pine Key area was harvested from 1936 to 1947, before the Park was established. The trees you see on the field trip are second growth since that time.
Just as we talk about endangered species, we can talk about endangered habitats. More than 98% of the Dade County pine forests have been removed. The few pine stands remaining have been weakened by genetic isolation and root damage, attacked by insects, stressed by dropping ground water levels, and badly damaged by Hurricane Andrew. The Dade County pinelands are a critically endangered habitat!
A healthy pineland requires recurring fire. The thin soil is enriched by the nutrients released after a fire. Slash pine seeds germinate quickly in the ashes. Fire burns away shrubby under growth, exposing young pine trees to the sun. Native slash pines have a protective covering over their developing buds, and layers of flaky bark that protect them during the heat of a burn. Notice how the older, tall pine trees have dropped their lower limbs; fire is unlikely to move into their crowns.
Here in Everglades National Park, and in Big Cypress National Preserve, fire is used as a tool to ensure the continuation of the pineland habitat. Lightening-caused fires that do not threaten buildings are allowed to burn. If necessary, park rangers will start carefully controlled fires to remove invading plants. Plots in Long Pine Key are burned about every three to five years. Students can easily find blackened bark and stumps, evidence of past fires.
Slash pine is the dominant tree, but the pinelands are habitat for many unique plants. (This area has some of the rarest plant species in Florida). Saw palmetto and cabbage palm (aka sabal palmetto) grow out of the rocky crags. They, too, are adapted for fire, putting forth new fronds from a woody heart that grows close to the ground. The prickly leaves and lavender flowers of the thistle will catch students' attention. You might also introduce them to the rough velvetseed. It lives up to its name and is fun to touch. The leaves feel like sandpaper.
Compare the leaves in the pinelands to those that grow in familiar well-watered yards or school grounds. Pineland forest habitat is a bright, dry place. Most plant species growing here have adaptations for conserving water. Leaves are protected from water loss with waxy, tough surface coverings.
While the morning hike features easy wildlife viewing, the afternoon part of the field trip takes the students to two types of forest with an abundance of plant life. This is an excellent opportunity to review some of the physical properties that characterize habitats: temperature, humidity, light, and wind speed. Notice how different these properties are in the adjoining high ground habitats. The broad-leaved trees growing in hammocks create a shadier, cooler, calmer, and more humid environment which in turn influences the kinds of wildlife (e.g. snakes, snails, and birds) that might be found there.
Even if you are a confident botanist, it's a mistake to try to name all the plants you'll be seeing. Students will respond best if you focus on just a few readily identifiable species. We especially recommend that you teach students to identify poisonwood and poison ivy. (See page 17 for more information on these and other species that pose safety concems.) Try to do this with minimum fuss, as we notice students have an exaggerated fear of these plants. Once they know what not to touch, students can begin to handle leaves and bark on other plants found throughout the area. Emphasize that plants should be examined without picking them.
|The shady darkness of the hammock is a dramatic contrast to the glare of the pinelands. A hammock is a hardwood forest habitat that thrives on elevated ground in the Everglades. Hardwood means just what it says; the wood is hard. Pines, in comparison, have soft wood.|
In South Florida, where frosts are rare, hammocks include many kinds of trees native to the West Indies. Here tropical species like pigeon plum, gumbo limbo, mahogany, and several kinds of bromeliads can survive. The hammock habitat is characterized by high humidity and deep shade. The ground underfoot is soft and spongy from the accumulation of decades of fallen leaves. A faint skunk-like, but not unpleasant, odor scents the air. This aroma is emitted by one of the common hammock tree species, the white stopper. (It gets its name for its use by pioneers as a treatment for diarrhea!)
Just as the trees are tropical, so are some of the animals found in South Florida hammocks. Zebra butterflies patrol the pathway you'll walk. Their shape is distinctive. They are members of a tropical family of butterflies called "long wings" that are found throughout Central and South America. Tree snails, close relatives of snail species that live in Cuba, are also seen. They graze during moist times on the algae and lichens that cover smooth-barked trees. During the dry winter months, when most school groups visit, tree snails have often sealed themselves in one spot to conserve moisture. Touching them roughly will dislodge them, and may kill them.
Native people, including Calusa Indians who lived here long ago, often set up camp in cool, shady hammocks. The habitat is an attractive one for people. Many of the hammocks that dotted the Atlantic Coastal Ridge have been destroyed, eaten away as cities grew. However, little patches hang on around some schools, city parks, and neighborhoods.
The lake that adjoins the Long Pine Key picnic area is the result of human activity. It was excavated to provide material for constructing the main park road. Although the lake isn't strictly natural, its shoreline supports a characteristic Everglades mini-habitat, periphyton. Periphyton is the name given to the complex association of algae that frequently forms a mat-like covering in the marshes of the Everglades. (Visiting Shark Valley, or taking a slough slog, will allow you to see periphyton in a more natural setting.)
Snails and plant-eating fish graze on periphyton, placing it at the very base of the food chain. The spongy structure of the mat also holds water well, sustaining small life forms through the dry season. The kinds of algae that thrive in the association are determined by water nutrient levels, so some of the controversy about Everglades restoration focuses on this green stuff. If the perphyton is doing well, the base of the Everglades food chain is operating properly!
Although periphyton is somewhat slimy, it isn't sticky or smelly. If time permits during your field trip, have your students sit on the lake shore while you step carefully down to the water's edge and pick up a handful of the mat. (The shore can be extremely slippery, so keep students back from the edge). Distribute a bit of periphyton to everyone to examine. Often small crustaceans and insects can be seen moving around in the algae. It's alive! Be sure to collect and return the periphyton to the lake edge.
The secretive giant cat called the Florida panther is sometimes present in the Long Pine Key area. Panthers hunt the deer that graze in Everglades grassy marshes. This pineland area adjoins a short hydroperiod marsh, a prime deer area. The pine forest offers cover for the panthers while they keep watch for deer. And during the heat of the day, panthers may retreat to sleep in the cool, dense hammock nearby. The panther's behavior demonstrates a concept ecologists call the edge effect. Edges have high concentrations of wildlife because animals can move easily between habitats which offer the different resources, food and shelter in this case, that they need. Since panthers prefer to move about when light levels are low, it's very unlikely that you will see one during a field trip.
Park rangers have found from experience that most visitors appreciate the opportunity to listen to the natural sounds and silence found in a large wilderness such as Everglades National Park. However, it's a little tricky guaranteeing this experience when managing thirty excited students! Your class ranger will make suggestions on where and when to stop your group for a listening break. Encourage the students to close their eyes. This will better focus their hearing. Once again, classroom discussion before hand about what to expect on the field trip, will prepare your group to be quiet and attentive during this special time.
The understory of the pine forest usually includes poisonwood, gumbo limbo, satin leaf, lysiloma, and other exampes of shrub-sized hammock trees. If fire is surpressed, these trees will begin to mature and shade out the young pines. After five to ten years the pineland may begin to resemble the other type of high ground habitat, a hammock. Also, when fire is suppressed the amount of material to burn increases. A fire burning through such heavy accumulated fuel may be hot enough to kill some pines plus the pineland ground cover.